Abstract. Using results from four coupled global carbon cycle-climate models combined
with in situ observations, we estimate the effects of future global warming
and ocean acidification on potential habitats for tropical/subtropical and
temperate coral communities in the seas around Japan. The suitability of
coral habitats is classified on the basis of the currently observed regional
ranges for temperature and saturation states with regard to aragonite
(Ωarag). We find that, under the "business as usual" SRES A2
scenario, coral habitats are projected to expand northward by several
hundred kilometers by the end of this century. At the same time, coral
habitats are projected to become sandwiched between regions where the
frequency of coral bleaching will increase, and regions where Ωarag will become too low to support sufficiently high calcification
rates. As a result, the habitat suitable for tropical/subtropical corals
around Japan may be reduced by half by the 2020s to 2030s, and is projected
to disappear by the 2030s to 2040s. The habitat suitable for the temperate
coral communities is also projected to decrease, although at a less
pronounced rate, due to the higher tolerance of temperate corals for low
Ωarag. Our study has two important caveats: first, it does not
consider the potential adaptation of the coral communities, which would
permit them to colonize habitats that are outside their current range.
Second, it also does not consider whether or not coral communities can
migrate quickly enough to actually occupy newly emerging habitats. As such,
our results serve as a baseline for the assessment of the future evolution
of coral habitats, but the consideration of important biological and
ecological factors and feedbacks will be required to make more accurate
projections.